The Humber collects from about 750 creeks and tributaries in a fan-shaped area north of the city.The footprint created by this system as it flows southwards to Lake Ontario
is known as the Humber River watershed. The main source of the river shares a limited geographical region near Orangeville, known as the "Headwaters" with three other well known drainage systems
in southern Ontario. These are the Credit, Grand and Nottawasaga rivers. Of the four rivers giving the area this name, only one, the Nottawasaga, flows north.

The Humber is a complex system consisting of three branches and many tributaries, most of which are unnamed.
{"Humber Watershed Map"}

One main branch runs for about 100 km from the Niagara Escarpment in the northwest, while the main branch arises in the Oak Ridges Moraine close to Mono Mills east of Orangeville, Ontario,

The smaller east branch starts in the Lake St. George & Lake Wilcox area
in the Oak Ridges Moraine to the northeast near Aurora, Ontario.

The three branches join north of Toronto and then flow in a generally southeasterly direction into Lake Ontario at what was once the far western portions of the city. This is just east of
Sir Casimir Gzowski Park and Humber Bay Park East.